SAN FRANCISCO — The San Francisco Ethics Commission opened its historic inquiry into Sheriff Ross Mirkarimi’s fitness for office Tuesday with a tedious tussle over potentially dramatic evidence.

Mayor Ed Lee suspended Mirkarimi in March without pay and is seeking his permanent ouster after the sheriff pleaded guilty to a misdemeanor domestic violence charge.

This is the first time the 19-year-old ethics commission has convened a trial-like hearing to determine whether an elected official should be removed from office. It will forward its recommendation to the Board of Supervisors, which needs the votes of nine of 11 members to remove Mirkarimi. The mayor and his lawyers are asking for a removal recommendation.

Mirkarimi was sworn as sheriff in January after winning election in November. He previously served seven years on the Board of Supervisors.

Mirkarimi sat stoically in the front row throughout the four-hour, 30-minute proceeding while the mayor’s lawyer called him a “convict” and argued for the inclusion of an emotional video of his wife tearfully displaying a bruised bicep.

The five-member commission put off deciding several key issues, such as the admissibility of the tape, until further arguments are made. The hearing is to reconvene on June 28 and could feature the live testimony of Mirkarimi. The mayor is also expected to testify live at some point as well.

Mirkarimi’s woes began on the afternoon of Dec. 31 when he and his wife, Eliana Lopez, got into an argument over whether she could travel to her native Venezuela with their three-year-old son, Theo.

Mirkarimi admitted bruising her arm with an overly firm grip. He pleaded guilty to misdemeanor false imprisonment in exchange for the dropping of three other misdemeanor charges. He was sentenced to probation and counseling.

Lopez and her son departed for Venezuela March 25 and have not returned. A judge has given Mirkarimi permission to visit his son, but he still under a court-order to stay away from Lopez.

Lopez is expected to submit written testimony to the commission. Lopez has said she asked her next-door-neighbor Ivory Madison to record her bruise in case she and Mirkarimi divorced and got into a custody dispute.

Lopez said she never intended for the video to be made public. A superior court judge later ruled that the video could be used in a criminal trial, a point ethics Commissioner Paul Renne made when Mirkarimi’s attorney, Shepard Kopp, argued for its exclusion from the current proceedings.

“That issue was incorrectly decided,” Kopp countered. The commission will rule on the tapes admissibility later.

The hearing will also featuring dueling law enforcement experts.

San Diego Police Chief William Lansdowne has submitted written testimony and expected to appear live later this month to argue that Mirkarimi is unfit to serve as sheriff.

“A top law enforcement officer — a sheriff or chief of police — is held to the highest standard and must lead by personal example,” Lansdowne said.

On the other side, former San Francisco Sheriff Michael Hennessey, who Mirkarimi succeeded after Hennessey declined to run for a ninth term, said Mirkarimi’s subordinates can carry out his orders while he serves probation.

“My opinion is also that the fact that Sheriff Mirkarimi has suffered a misdemeanor conviction for which he is on probation will not impair him from performing the duties of Sheriff of San Francisco,” said Hennessey, the longest-serving sheriff in San Francisco history.

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